Bipolar batteries are known in the art, see Tatematsu US 2009/0042099, incorporated herein by reference in its entirety. Bipolar batteries provide advantages over other battery designs such as scalability, relatively high energy density, high power density and design flexibility. Bipolar batteries comprise a number of bipolar plates and two monopolar end plates. A bipolar plate comprises a substrate which is in the form of a two sided sheet having a cathodic material, often referred to a Positive Active Material (PAM), on one surface and on the opposite side is an anodic material, often referred to a Negative Active Material (NAM). A conductive sheet may be disposed between the substrate and the anodic material or cathodic material. The bipolar plates are arranged in a stack such that the anodic material of one plate faces the cathodic material of the next plate. In most assemblies, there is a battery separator located between the adjacent plates which allow an electrolyte to flow from cathodic material to the anodic material. Disposed in the space between the plates is an electrolyte, which is a material that allows electrons and ions to flow between the anodic and cathodic material. The adjacent surfaces of the bipolar plates with the separator and the electrolyte disposed between the plates form an electrochemical cell wherein electrons and ions are exchanged between the anodic material and the cathodic material. The structure of the battery is arranged such that each cell formed by the bipolar plates is sealed to prevent flow of electrolyte out of the cell. The structure used to seal each electro-chemical cell is in contact with the portion of the plates not having anodic or cathodic material on the substrate. In addition, the battery separator can extend beyond the portion of the substrate having the anodic and cathodic material disposed thereon to aid in sealing the cells. Each cell has a current conductor connected to the cell to transmit electrons from the cell to one or more terminals from which the electrons are transmitted to a load, in essence another system that utilizes the electrons in the form of electricity. In some embodiments, the current conductor in a cell is the conductive sheet which is in contact with additional current conductors which transmit the electrons to the terminals of the battery. At each end of the stack is a monopolar plate having either anodic material or cathodic material disposed on one face. The material on the face of the monopolar plate is selected to form a cell with the opposing face of the bipolar plate at that end of the stack. In particular if the bipolar plate facing the monopolar plate has cathodic material on the face of the plate then the monopolar plate has anodic material on its face and vice versa. In conventional designs, the stack(s) of battery plates are disposed in a case which is sealed about the stack of plates and has one or more pairs of positive and negative terminals located on the outside of the battery, each pair is connected to a current conductor further connected to one of more cells as described herein.
Despite the advantages of bipolar battery assemblies, the disadvantages of bipolar battery assemblies have prevented them from being commercialized. Bipolar batteries during operation generate significant internal pressures due to expansion and contraction of anodic and cathodic material, gas evolution during the electrochemical process and heat generated. Because bipolar batteries are scalable higher pressures in the cells can be generated. In addition, the heat evolved can exacerbate the pressures generated and can result in runaway reactions which can generate heat levels that damage the materials of construction of the batteries and render the batteries non-functional. The pressures can cause the seals about the electrochemical cell to rupture and render the cells and battery nonfunctional. Commonly owned patent application titled BIPOLAR BATTERY ASSEMBLY, Shaffer I I, et al. US 2010/0183920, incorporated herein by reference in its entirety, discloses solutions to these problems through improved edge sealing assemblies and bipolar plate designs.
There are still needs to be addressed before bipolar batteries can be commercialized and the full potential of this technology can be achieved. In particular, bipolar battery designs that handle the heat and pressures generated in operation in an improved manner are needed. Present and future users of batteries often have limited packaging space available for batteries and batteries that can be adapted to available packaging space are needed. Most systems using batteries also desire lighter weight batteries and bipolar batteries which exhibit lower weights, are desired. Bipolar battery designs that reduce parts and complexity, such as special parts used for sealing of the electrical cells and separate cases are desired. The ability to mass produce battery stacks and the ability to electrically connect the battery stacks to increase power output would be beneficial. Also advantageous would be the ability to electrically connect varying numbers of similarly produced battery stacks (e.g., two stacks, three stacks, four stacks having the same number of bipolar plates) to allow for varying configurations of bipolar batteries with increased power output. Batteries that minimize volume and increase power output are desired, that is batteries with enhanced power density are desired. Methods for battery assembly that are simpler and utilize known manufacturing techniques and achieve the abovementioned goals are needed. Batteries that can be scaled to fit the user needs are needed.